The document describes the architecture of the Symbian OS. It discusses the four main layers: the UI Framework layer, which provides frameworks for building user interfaces; the Application Services layer, which provides application support services; the OS Services layer, which implements core OS functionality like graphics and connectivity; and the Hardware layer, which interacts directly with device hardware. Each layer is broken down into further components, frameworks and services that work together to power Symbian smartphones. Diagrams are provided to illustrate the organization and relationships between the different parts of the Symbian OS architecture.

1. Bharati Vidyapeeths College of Engineering,
Kolhapur
Symbian OS Architecture
Prepared By: Ms. Priya B. Pandharbale

2. Figure 1: First Symbian Phone, the Nokia 9210 Communicator
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3. User interface
Figure 2: User Interface for the Nokia 7650
Figure 3: User Interface for the Nokia 9210 Communicator
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4. Layered Architecture Of Symbian OS
Figure 4: Symbian OS Architecture
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5. UI Framework Layer
The topmost layer of Symbian OS
provides the frameworks and libraries
for constructing a user interface,
including the basic class hierarchies for
user interface controls, and other
frameworks and utilities, including
concrete widget classes used by
interface components.
Figure 5: UI framework Layer
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6. Component Collection in UI
Figure 6: Component collections in the UI Framework layer
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7. UI Application Framework Collection
Figure 7: UI Application Framework collection
• The Uikon: component provides a concrete framework for user interface and application
creation. Applications, typically, should not derive directly from Uikon classes. Instead, they
should derive from equivalent classes provided by the variant user interface, because these
provide the appropriate look and feel and other device-specific behavior. However,
applications implement virtual methods inherited from Uikon and call inherited methods.
• The Control Environment (CONE) : provides a control hierarchy and environment. It
provides policy-free abstract controls and control context, as the basis for interaction between
the user and the application. It includes the application interface to user and keyboard events
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and View Server encapsulation.

8. Continued..
The FEP Base component provides base classes for creating FEPs. FEPs selectively intercept and
preprocess user input events, which are returned to the system as simplified events for handling by
applications, to enable keyboard mapping, multitap keyboard input, handwriting recognition, voice
recognition and other input preprocessing.
The UI Look and Feel component defines the look-and-feel properties of the user interface. It defines
standard methods (i.e. an API) for which user interface customizers provide an implementation in
the UikLaf library of a variant user interface. The role of the user interface LAF component is to
provide other parts of the application framework with a way of requesting look-and-feel information
from a variant user interface, including the layout and behavior of windows; which bitmaps and
fonts to use; and the location of various resource files.
The Uikon Error Resolver Plug-in is a resource file that maps system error numbers to helpful error-
text strings, which a variant user interface extends and customizes. Errors are flagged when a user
interface thread leaves normal execution inside the active scheduler of an application.
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9. UI Support Collection
UI Support collects miscellaneous frameworks, utilities and libraries that are used by variant user
interfaces and which, in some cases, may also be used directly by applications.
Figure 8: UI Support Collection
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10. Continued….
• The Graphics Effects component supports flicker-free animation of windows and window
contents and composition of animation effects with other graphics objects, to enable GUI
special effects.
• The UI Graphics Utilities component consists of libraries used by user-interface framework
components, the variant user interface and applications. They provide color, font, icon, text,
drawing, and number conversion utilities.
• The Animation component enables animated effects to be included in the normal drawing of
a window by a client or to be managed server side as a sprite. It also defines a plug-in
interface enabling new animation types to be created.
• The BMP Animation component is a Window Server plug-in utility that enables bitmap-
based frames sequence animation. Bitmap-based animations are rectangular.
• The Grid component is a simple layout engine providing presentation, print preview and
printing for complete spreadsheets and for spreadsheet cells, rows and columns. It is now
considered a legacy Component.
• The Clock component is a shared library for creating animation-based digital and analog
clocks, used by user interfaces and applications.
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11. The Application Services Layer
Figure 9: Component Collections in the Application Services layer
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12. The Application Services Layer
The Application Services layer provides support independent of the user interface for applications on
Symbian OS. These services divide into three broad groupings:
• System level services : system-level services used by all applications, for example the
Application Architecture or Text Handling
• Application Framework
• Application Launch Services
• Multimedia Protocols.
• Application services and engines: services that support generic types of application and
application-like services, for example personal productivity applications.
• Data Sync Services
• Device Management
• Client Provisioning
• PIM App Services: services based on more generic but application-centric technologies, for
example mail, messaging and browsing.
• Other Application Services
• Office Application Engines
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13. OS services Layer
The OS Services layer provides the servers, frameworks and libraries that implement the core operating
system support for graphics, communications, connectivity, and multimedia, as well as some generic
system frameworks and libraries.
Figure 10: Blocks of OS Services Layer
There are four major blocks by broad technology type:
• Generic OS Services
• Multimedia and Graphics Services
• Connectivity Services
• Comms Services
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14. Generic OS Services
This block provides a small number of generic services for use directly by applications, as well as
some specific programming libraries intended for application and system use (including for use by
the user interface and application support layers above).
The logging and task-scheduling services are used by
applications as well as by system components.
• The C Standard Library, providing a basic POSIX
environment, is used by system components (for example,
Java) and is also useful to those porting software from
other platforms.
• There are libraries and frameworks supporting
cryptographic and certificate-based security, ncluding the
key and certificate stores.
Figure 11: Generic OS
Services block
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15. Multimedia and Graphics Services
This block provides all graphics services above the level of hardware drivers and provides the
frameworks supporting multimedia services.
• It provides windowing, event handling, bitmap and
vector graphics support including all font, drawing
and bitmap functions, as well as low-level support for
WYSIWYG printing.
• It defines a comprehensive set of multimedia APIs
and provides a framework for implementation. It
includes camera and broadcast tuner APIs, sound
capture and recording APIs, still and moving image
capture and recording APIs, display and play APIs,
and conversion and manipulation APIs.
Figure 12: Multimedia and Graphics
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16. Connectivity Services Block
• This block provides the device-side support for connectivity services, for example backup and
restore, file transfer and browsing and application installation.
The connectivity architecture provides a framework within which the
device-side of TCP/IP-based device-to-host services can be created.
Figure 13: Connectivity
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Services Block

17. The Comms Services Block
• ‘Comms’ (or communications), in this context, really means ‘data communications’ moving
data between different devices over direct connections or networks.
Figure 14: The Comms Services Block
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18. Comms Framework sub-block
The Comms Framework provides the generic
infrastructure that supports all communications
services.Most importantly,
•It includes the Comms Root Server, which is the
‘meta’ process server for all communications
services.
• Esock Socket Server which provides the generic,
sockets-style interface used to access all
communications services.
Figure 15: Comms. Framework sub-block
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19. Telephony Services sub-block
•The Telephony Services are based on the ETel
Telephony Server that provides support for 2G, 2.5G
and 3G mobile phone networks, including
SM/GPRS/EDGE/UTMS (2G/2.5G/3G) and
CDMA/CDMA2000 (2G/2.5G/3G North America).
•GPRS and EDGE are the incremental packet data
and ‘go faster’ increments to GSM; UMTS and
CDMA2000 are the respective GSM and CDMA
evolutions to 3G.
Figure 16: Telephony Services sub-block
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20. Networking Services sub-block
Networking Services provides packet-based network
services with Ethernet emulation and includes the
TCP/IP stack implementation, secure networking
extensions including TLS/SSL and IPSec, which
support secure browsing and VPN gateways, together
with a variety of application-level Internet services
including FTP and HTTP. (FTP does not expose
public APIs.)
All networking services are designed to be
virtualized over telephony, serial or short-link
bearers. Support for Wi-Fi appears for the first time
in Symbian OS v9 (although licensees have Figure 17: Networking Services sub-block
introduced Wi-Fi-enabled phones based on earlier
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releases).

21. Short-link services sub-block
Short-link services provides USB, Bluetooth and
nfrared services including support for the OBEX
inary object protocol, USB class support that enables
a Symbian OS phone both to use and serve as a USB
host, and full implementations of the IrDA and
luetooth protocol stacks.
Figure 18: Short-link services sub-block
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22. References
• The Symbian OS & Architecture Sourcebook
-By Ben Morris